1. Field of the Invention:
This invention relates to an apparatus for mounting a flat package type IC on a printed circuit board, and more particularly to an apparatus for automatically mounting a flat package type IC on a printed circuit board.
2. Description of the Prior Art:
Recently, digitized electronic apparatuses have began to be mass-produced, with the expanded demand for the miniaturization and high performance electronic apparatus. In many of such apparatuses, flat package type ICs of large scale and high integration degree are mounted on a printed circuit board (hereinafter, abbreviated as "PCB"). Attempts to automatize the process of mounting a flat package type IC on a PCB have been conducted. However, it is difficult to automatically mount a flat package type IC of large scale (number of leads: 100 to 400) and high integration degree (lead interval: 0.6 to 0.4 mm).
FIG. 10 illustrates a prior art apparatus of automatically mounting a flat package type IC in which apparatus an industrial robot is used. In the apparatus of FIG. 10, a feed station 21, a lead recognition station 22, a mount station 24, and a land recognition station 26 are arranged along the orbit 23 of an industrial robot (not shown). An IC to be mounted is fed to the feed station 21, and is securely held by a hand of the industrial robot. The lead recognition and land recognition stations 22 and 26 are respectively provided with a camera (not shown) which is fixed to a predetermined position. A PCB to which the IC is mounted is placed on an XY table 25 which moves from the land recognition station 26 to the mount station 24. The PCB held by the robot is transferred from the part feed station 21 to the lead recognition station 22, then the camera of the station 22 shoots the IC to obtain an entire image 32 of leads of the IC (FIG. 11). On the other hand, the camera of the land recognition station 26 shoots the PCB to obtain an entire image 33 of lands of the PCB (FIG. 12).
The two images 32 and 33 are processed by a known image processing technique to obtain a relative positional relation between a specific lead and the corresponding land. In FIGS. 11 and 12, an image coordinate 31, a rotational deviation .DELTA..theta..sub.a of the lead from the X-coordinate, and a rotational deviation .DELTA..theta..sub.b of the land from the X-coordinate are shown. From the obtained positional relation, the linear correction component and rotational correction component of the movement of the robot hand are calculated. Then, both the IC held by the robot hand and PCB placed on the XY table 25 are transferred to the mount station 24, and the IC is placed on the PCB to be mounted thereon. In this process, the movement of the robot hand holding the IC is corrected in accordance with the calculated linear and rotational correction components, so that leads are suitably positioned with respect to corresponding lands.
The above-mentioned prior art apparatus may conduct adequately a mount process for a flat package type IC of relatively small scale or low integration degree, but cannot mount a flat package type IC of large scale and high integration degree because this apparatus cannot provide an entire image of leads of such a relatively large scale IC.
This problem in a prior art apparatus may be overcome by disposing a plurality of cameras at the lead recognition station 22. Even if an entire image of leads can be obtained by combining several camera images, it is still difficult to obtain accurately the linear correction component and rotational correction component of the movement of the robot hand, because such a large scale IC has a large number of leads. Moreover, leads are not always oriented in the predetermined directions, resulting in that an accurate mount is not performed only by one linear and rotational correction. This also applies to lands of a PCB on which a large scale IC is to be mounted.
When a large scale IC is mounted on a PCB, further, many precise processes including other various inspections such as those on the bend, alignment and number of leads must be conducted. It is impossible to conduct these processes by a prior art apparatus such as shown in FIG. 10.